I have a problem with my 2000 Expy 5.4 2WD. Sorry it's a bit of a long tale to get to where I am, but here goes.

My college student son drives this vehicle. A week or so ago he was driving home at night when the lights began to flicker and the battery light on the dash came on. I tested the alternator output while running and found it didn't change at all from the battery output while still. So I thought the alternator had gone bad as it has 170K on it and it was the original alt.

Yesterday we replaced it. We also replaced both battery cables as they were pretty corroded, even inside the insulation. Went to start the engine and nothing happened. Shut off the ignition and checked the cables and found the one going from the battery to the relay/solenoid on the firewall was pretty warm.

My son had accidentally hooked the cables up wrong under the truck. He had put the wire that grounds to the frame rail on the starter and vice versa. I'm mentioning this in case it has anything to do with my current problem.

After fixing the wiring, we started the engine. It started and ran correctly, but the new alternator still wasn't charging. After doing some digging I found that the 20A fuse for the alternator (in the engine fuse box) was blown. I kinda had a "smack my forehead" moment thinking this was the problem all along and I just bought an alternator for nothing.

So I swapped the fuse and started the engine. Things went really wrong then. The engine made an odd noise for a couple seconds, then there was a louder sound, like a mixture of a screech and a pop, and then it ran normally. I didn't like the sound of that so I shut it off.

I got around to the engine bay and smelled a burning smell. Felt all of the cables in the engine bay and none were warm. Climbed underneath to the starter and found that the solenoid on the starter was hot. I'm afraid the noise I heard when the engine started may have been the starter not disengaging, but I'm not sure. After the screech/pop, the engine sounded normal.

I tried to tap the starter after it cooled down, nothing. So the solenoid, starter or both, are fried.

So now I don't know what to do. I can replace the starter, but if there is another electrical problem, that may not be the end of this. Is there a short somewhere that started all this? Why did the fuse blow to start with? Were the alternator or battery cables the problem, and the starter blew coincidentally, or because of those cables being reversed momentarily hurt it? It did however start normally two or three times after that.

I'm a pretty good shadetree wrench, I have several classic cars and have done everything on them, including engine and transmission rebuilds. And I've worked on my daily drivers much more that I've had shops work on them. But electrical issues are my Achilles Heel. Especially on newer vehicles. I'm not sure whether to keep messing with this or give in and take it to a shop. Any ideas what could be going on here?

 

To me it sounds like you had several issue converge on you all at once. The alternator, cables, and starter might have already been on the verge of going bad and when one went it took the others with it. I would remove and bench test the starter to see if it's working correctly and go from there.

 

Thanks alloro. I removed the starter and bench tested it, it's dead. I ordered another one that should be here this week. I'm going to replace the relay/solenoid on the firewall and the alternator cable too, if I can get it from the dealer. Can't find it at the aftermarket places.

Hopefully, that will eliminate all of the potential trouble spots. I just hope there's not a short or other type of problem somewhere that fries some of this new stuff.

 

Keep us updated.

 

The firewall starter relay only supplies ignition switched 12v to one stud (passenger side one), the remaining stud acts as a centralized power distribution point for everything. When I built my new mega fuse block, I rerouted things so the main battery cable went directly to the block, then has a stainless steel link bar to the other mega fuse (similar to stock) and a short jumper cable over to feed the starter relay. One fewer cable, and unrustable connections at every point.

Alt cable is just 4awg you can find anywhere. Starter relay on the firewall is a common design part and is really underworked. Check Texas Industrial Electric

 

I got the new starter and firewall solenoid in. Started it up and the new starter is hanging too. I tried two tests that seem to conflict, but maybe I just don't understand what I'm seeing.

I had my son start the engine while I kept my long nose pliers on the "S" connection wire on the solenoid. I was checking to see if the solenoid was still getting voltage after the engine started. I'm testing for a bad ign swith or some other upstream issue from the solenoid that's keeping the solenoid engaged. As soon as the engine started I pull the wire, but the starter stays engaged. So it's seems that's not the problem.

However, I pulled the "S" wire and attached my meter positive to it and the negative to chassis ground. With the ign switch in the Start position, it's getting 12V as expected. But when the ign switch is in Run, it's still getting 4V or so. Is this normal?

 

I pulled the new starter and bench tested it to make sure it was retracting. It is. I'm flummoxed.

 

One more test. With the starter removed, I got underneath and put my multimeter between the solenoid (on the starter) hot wire and ground. This is the small wire that activates the solenoid, not the battery power. Had my son turn the ign switch from Off to Run. No power to solenoid wire as it should be. Had him switch to Start, got 12V. Let the switch go back to Run, and the voltage did not immedaitly go to 0, but kind of "wandered" down, from 12V to 8 to 4, etc. I though maybe this was keeping the gear engaged to the flywheel.

So I put the starter on the ground below the truck. Used jumper cables and wire to connect it as it would be if it was installed. Hit the starter and let go. The gear extended from the housing and withdrew as soon as the switch was released.

So now I'm wondering if there is a mechanical binding of the gear to the flywheel. Does anyone have to shim starters the way we did on classic cars? There was no shim when I pulled the old one off. I figured with today's tolerances that might be a thing of the past.

 

Your gut feeling is correct, no shimming is necessary. The starter is behaving properly, the firewall relay is too. If the voltage is 'going downhill' on the firewall relay's S terminal, your ignition switch is the problem. It should immediately cut power to the starter when you let it return to RUN. It's why they call it Ignition Switch, not Ignition Dimmer

I suspect this 'downhill' behavior is what toasted your old starter, as it just couldn't get it up...